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[HOW TO] SecureBootModel changes in OpenCore 0.7.2

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Apple Secure Boot is the technology used in Macs to verify the integrity of the operating system at boot: boot loader > kernel > system volume snapshot. If this check fails, macOS won't boot. Apple Secure Boot only works during the boot process, once macOS is running it no longer performs any function. It is highly recommended to read the Dortania guides: applesecureboot.md, uefisecureboot.md and vault.md.

OpenCore SecureBootModel


Apple defines 3 Secure Boot modes:
  • Full Security: Only allows to boot the installed operating system or another signed version of macOS in which Apple currently trusts. It also checks the integrity of the installed version. If the check fails, the system offers to reinstall macOS or boot from a different disk.
  • Medium Security: Checks that the installed version of macOS is legitimate but not the integrity of the system. Lets you boot any signed version of macOS in which Apple has ever trusted.
  • No Security: other systems or versions different from those mentioned in the secure options are allowed. There are no requirements on the boot operating system.
Apple Secure Boot state on Intel-based Macs can be obtained from NVRAM:
nvram 94b73556-2197-4702-82a8-3e1337dafbfb:AppleSecureBootPolicy

If the variable is found, it can be one of the following:
  • %02 - Full Security Mode
  • %01 - Medium Security Mode
  • %00 - No Security Mode
If the variable is not found, Apple Secure Boot is not supported.

OpenCore has a SecureBootModel key that adjusts the Apple Secure Boot mode to make it similar to Macs. This key has been changed in OpenCore version 0.7.2.
  • In OpenCore 0.7.1, failsafe value for SecureBootModel is Default, this value sets Apple Secure Boot hardware model as j137 (iMacPro1,1 December 2017 macOS 10.13.2). This means that macOS versions older than 10.13.2 cannot be installed with this SecureBootModel value.
  • In OpenCore 0.7.2, failsafe value for SecureBootModel remains Default, but this value sets Apple Secure Boot hardware model as x86legacy, new value (not existing in previous versions) that corresponds to macOS 11 Big Sur and 12 Monterey on hardware without T2 chips (hackintosh machines) and virtual machines.
Notice that with OpenCore 0.7.2:
  • x86legacy is designed for machines without T2 chip* with Big Sur and Monterey
  • j137 doesn't work on Monterey
  • j137 is the recommended value for macOS 10.13.2 through 10.15.x
  • systems older than macOS 10.13.2 must set SecureBootModel=Disabled
  • users who don't want to have Apple Secure Boot for any reason can set SecureBootModel=Disabled, even in Big Sur and Monterey.
*According to Apple, these Mac computers have Apple T2 security chip:
  • iMac (2020)
  • Mac Pro (2019)
  • Mac Pro (Rack, 2019)
  • Mac mini (2018)
  • MacBook Air (2020)
  • MacBook Air (2019)
  • MacBook Air (2018)
  • MacBook Pro (2020)
  • MacBook Pro (2019)
  • MacBook Pro (2018)
  • iMac Pro (2017).
Valid values in OpenCore 0.7.2 (all are models with T2 but x86legacy and disabled):
  • Default — Recent available model, currently set to x86legacy
  • Disabled — No model, Secure Boot will be disabled
  • j137 — iMacPro1,1 (December 2017) Minimum macOS 10.13.2
  • j680 — MacBookPro15,1 (July 2018) Minimum macOS 10.13.6
  • j132 — MacBookPro15,2 (July 2018) Minimum macOS 10.13.6
  • j174 — Macmini8,1 (October 2018) Minimum macOS 10.14
  • j140k — MacBookAir8,1 (October 2018) Minimum macOS 10.14.1
  • j780 — MacBookPro15,3 (May 2019) Minimum macOS 10.14.5
  • j213 — MacBookPro15,4 (July 2019) Minimum macOS 10.14.5
  • j140a — MacBookAir8,2 (July 2019) Minimum macOS 10.14.5
  • j152f — MacBookPro16,1 (November 2019) Minimum macOS 10.15.1
  • j160 — MacPro7,1 (December 2019) Minimum macOS 10.15.1
  • j230k — MacBookAir9,1 (March 2020) Minimum macOS 10.15.3
  • j214k — MacBookPro16,2 (May 2020) Minimum macOS 10.15.4
  • j223 — MacBookPro16,3 (May 2020) Minimum macOS 10.15.4
  • j215 — MacBookPro16,4 (June 2020) Minimum macOS 10.15.5
  • j185 — iMac20,1 (August 2020). Minimum macOS 10.15.6
  • j185f — iMac20,2 (August 2020). Minimum macOS 10.15.6
  • x86legacy — Macs without T2 chip and VMs. Minimum macOS 11.0.1.
iMac19,1 (March 2019 - Minimum macOS 10.14.4) isn't in the list because it has no T2 chip.

Of course, you can also set Secure Boot Model to the value, from the list above, that corresponds to the macOS version you want to boot (example j160 for macOS Catalina 10.15.1). If you are suspicious of old operating systems, you can always put the model that supports only the macOS versions that you need and not the older ones. For example, j140k will filter 10.13 and lower, j152f will filter 10.14 and lower, x86legacy will filter 10.15 and lower.

Apple Secure Boot in the hackintosh

How to get Apple Secure Boot in the Hackintosh? OpenCore provides 3 keys to enable Secure Boot:
  • Misc >> Security >> DmgLoading: to set load policy with DMGs in OpenCore; it can be Any (boot fails if Secure Boot is enabled), Signed and Disabled (both support Secure Boot)
  • Misc >> Security >> SecureBootModel: to set the Apple Secure Boot hardware model and policy; SecureBootModel (not Disabled) gives Medium Security, for Full Security you must use ApECID
  • Misc >> Security >> ApECID: Apple Enclave Identifier, to use personalized Apple Secure Boot identifiers and to have Full Security when paired with SecureBootModel.
For ApECID value, you must get a 64 bit integer randomly generated in a cryptographically secure way. You can use the urandom bash command in Terminal. This tool can generate a random 32 bit integer, if we run the tool twice and combine the 2 32-bit integers we get a 64-bit value. Copy this text into a file, save it with sh extension and run it with double click:
Bash:
#!/bin/sh
# first 32 bit integer
low32=$(od -An -N4 -tu4 < /dev/urandom)
# second 32 bit integer
high32=$(od -An -N4 -tu4 < /dev/urandom)
# joining the 2 numbers
long=$(($low32 + ($high32 << 32)))
# removing leading minus sign if exists
echo $long | sed 's/-//'
Now you can enter it under Misc -> ApECID in your config.plist.
Note: don't use random instead of urandom, it isn't cryptographically secure.

When using ApECID, SecureBootModel must have a defined value instead of default. I have found that x86legacy provides Medium Security and only values that correspond to Mac models that have T2 chip (example: j185, j137) allow you to personalize the boot volume and get Full Security. Remember that SecureBootModel and SMBIOS are different things, it is not mandatory to have the same Mac model in both keys and there are really no advantages or disadvantages if they are the same.

First time that macOS boots with an ApECID value you must personalize the boot volume. To do this:
  • boot into Recovery
  • be sure you have an Internet connection
  • open Terminal
  • bless --folder "/Volumes/HD/System/Library/CoreServices" --bootefi --personalize
    (replace HD with the name of your system volume)
  • reboot into macOS.
SecureBootModel and ApECID:
  • with SecureBootModel=Disabled>> no security (%00)
  • with SecureBootModel=x86legacy or any of the valid values >> medium security (%01)
  • with SecureBootModel= any of the T2 values plus ApECID non zero >> full security (%02).
Vault

It's a secure boot for OpenCore, digitally signing OpenCore.efi so no one can modify boot loader files except you.

config.plist
As first task, you must modify config.plist:
  • Misc >> Security >> Vault:
    - Basic: Requires just vault.plist file to be present, used for filesystem integrity verification
    - Secure: Requires both vault.plist and vault.sig files, used for best security as vault.plist changes require a new signature
  • Booter >> ProtectSecureBoot=Yes >> needed with Insyde firmwares for fixing secure boot keys and reporting violations.
CreateVault
Copy OpenCorePKG/Utilities/CreateVault folder next to the EFI folder inside the EFI partition. The resultant path must be: EFI partition/Utilities folder/CreateVault folder.
Bash:
.
├── EFI
│   ├── BOOT
│   └── OC
├── Utilities
│   └── CreateVault
│       ├── RsaTool
│       ├── create_vault.sh
│       └── sign.command
└──
Inside CreateVault there are 3 files: create_vault.sh, RsaTool and sign.command.
Run sign.command >> to generate a hash for each file in the EFI folder, write them to the vault.plist file and create a 256-byte signature of vault.plist that will be inserted into the OpenCore.efi file.

How to disable Vault?
  • Get a new copy of OpenCore.efi
  • Misc >> Security >> Vault >> Optional
  • Remove vault.plist and vault.sig.
UEFI Secure Boot option in BIOS

UEFI Secure Boot only allows to boot OS's that are signed and trusted. PC Bios comes with Microsoft keys as trusted. So, to boot Windows with Secure Boot, you need to enable Secure Boot in BIOS and to have Windows 10/11 keys (usually included in the motherboard firmware). But this is only for Windows. macOS has its own implementation Apple Secure Boot, this feature can be done with Secure Boot disabled in BIOS. So, these are 2 separate systems: PC BIOS Secure Boot and Apple Secure Boot.

Windows boots fine with Secure Boot enabled or disabled in BIOS. But Opencore only boots with Secure Boot disabled in BIOS (as expected). This is not important for users who only use macOS. But since Windows 11, nearing its final release, seems to require Secure Boot enabled in BIOS, it's important for users who want to have macOS and Windows together and plan to upgrade to Windows 11.

By default our hacks work with BIOS secure boot disabled since always, this is one of the BIOS options required to boot with OpenCore or Clover, but I wanted to find some not very complicated way of running OpenCore with PC BIOS Secure Boot enabled (if possible, probably not for now at least in a simple way). When booting OpenCore with Secure Boot mode enabled in BIOS, a warning saying "Secure boot violation. Invalid signature detected. Check secure boot policy in setup" is displayed by the firmware before OpenCore that fails and does not boot.

UEFI Secure Boot with OpenCore has its own post: [GUIDE] OpenCore and UEFI Secure Boot using Windows Subsystem for Linux.

Important note: at the moment it is not possible to have UEFI Secure Boot + Vault at the same time. Since both systems sign or modify the OpenCore.efi file, when the second applied modifies this file breaks the integrity kept by the first applied. It doesn't matter which of 2 is applied first, after doing digital signature + vault (or in reverse order) OpenCore doesn't boot with a corruption notice of OpenCore.efi.
 
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In OpenCore 0.7.1, failsafe value for SecureBootModel is Default, this value sets Apple Secure Boot hardware model as j137 (iMacPro1,1). This means that macOS versions released before the iMacPro1,1 model (December 2017, minimum macOS 10.13.2) cannot be installed with this SecureBootModel value.

In OpenCore 0.7.2, failsafe value for SecureBootModel remains Default, but this value sets Apple Secure Boot hardware model as x86legacy, new value (not existing in previous versions) that corresponds to macOS 12 Monterey on hardware without T2 chips.

Notice that with OpenCore 0.7.2:
  • Monterey requires x86legacy (Default now)
  • for Big Sur use x86legacy
  • j137 doesn't work with Monterey
  • j137 is the recommended value for macOS 10.13.2 through 10.15.x
  • users with systems older than iMacPro1,1 must set SecureBootModel=Disabled
  • users who don't want to have Apple Secure Boot for any reason can set SecureBootModel=Disabled, even in Monterey.
Valid values in OpenCore 0.7.2:
  • Default — Recent available model, currently set to x86legacy
  • Disabled — No model, Secure Boot will be disabled
  • j137 — iMacPro1,1 (December 2017) Minimum macOS 10.13.2
  • j680 — MacBookPro15,1 (July 2018) Minimum macOS 10.13.6
  • j132 — MacBookPro15,2 (July 2018) Minimum macOS 10.13.6
  • j174 — Macmini8,1 (October 2018) Minimum macOS 10.14
  • j140k — MacBookAir8,1 (October 2018) Minimum macOS 10.14.1
  • j780 — MacBookPro15,3 (May 2019) Minimum macOS 10.14.5
  • j213 — MacBookPro15,4 (July 2019) Minimum macOS 10.14.5
  • j140a — MacBookAir8,2 (July 2019) Minimum macOS 10.14.5
  • j152f — MacBookPro16,1 (November 2019) Minimum macOS 10.15.1
  • j160 — MacPro7,1 (December 2019) Minimum macOS 10.15.1
  • j230k — MacBookAir9,1 (March 2020) Minimum macOS 10.15.3
  • j214k — MacBookPro16,2 (May 2020) Minimum macOS 10.15.4
  • j223 — MacBookPro16,3 (May 2020) Minimum macOS 10.15.4
  • j215 — MacBookPro16,4 (June 2020) Minimum macOS 10.15.5
  • j185 — iMac20,1 (August 2020). Minimum macOS 10.15.6
  • j185f — iMac20,2 (August 2020). Minimum macOS 10.15.6
  • x86legacy — Macs without T2 chip and VMs. Minimum macOS 11.0.1.
Of course, you can also set Secure Boot Model to the value, from the list above, that corresponds to the macOS version you want to boot (example j160 MacPro7,1 for macOS Catalina 10.15.1). But x86legacy is mandatory for Monterey if you want Apple Secure Boot.
Thanks, @miliuco. Is there no setting for iMac 18,3 or should I choose something close to it from your list?
 

pastrychef

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I don't understand why j137 won't work with Monterey since real iMacPro1,1s don't have T2.
 
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I don't understand why j137 won't work with Monterey since real iMacPro1,1s don't have T2.
According to Apple's site (https://support.apple.com/en-us/HT208862), it does have a T2 chip.
Thanks, @miliuco. Is there no setting for iMac 18,3 or should I choose something close to it from your list?
The SMBIOS and secure boot model do not need to match. They're completely unrelated. Afaik, secure boot model has no effect once your within macOS. Choose based off of the OSes you want to boot, or just disable it. I'm keeping it disabled right now on my X1 Extreme, but only because I regularly boot between Catalina, Big Sur, and Monterey.

I'd recommend if your booting Big Sur+ only, just use default (x86legacy), and only choose j137 (or some other model) if you want to boot Catalina.

(inclusive)
High Sierra->Big Sur = j137 (or some other t2 model)
Big Sur->Monterey = x86legacy
 
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iMac18,3 (released in June 2017) is older than iMacPro1,1 so it is not on the list.
Facepalm. When I read iMacPro 1,1 in Miliuco's chart, my brain decided it was MacPro 1,1. Thanks.
 

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@miliuco Can you confirm:
  • The list above doesn't show all the Apple systems that contain a T2 chip.
  • Anyone using one of those system SMBIOS can choose to use the matching value from the list above for SecureBootModel.
  • They can also use 'j137' as a default value running High Sierra to Catalina.
  • Any one running Big Sur needs to use their system value, or x86legacy as a default value.
  • Any one running the Monterey Public beta needs to use x86legacy.
For example my iMac15,1 would use j137 when booting Catalina, but I would need to switch to x86legacy when booting Big Sur with OC 0.7.2.

Is that correct?

Is there a fuller list of systems with corresponding values for all the Apple models containing T2 chips? Or is this just the list of systems that the OpenCore developers have added to the system, with others to follow?


The part that still confuses me a little is this:
  • j137 is the recommended value for macOS 10.13.2 through 10.15.x
Is that the value everyone running High Sierra 10.13.2 through to Catalina 10.15.7 should use, even when their corresponding Apple system doesn't contain a T2 chip?

Will x86legacy work in these earlier versions of macOS on non-T2 systems?
 
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@Edhawk

The list above doesn't show all the Apple systems that contain a T2 chip >> although it only shows models starting at iMacPro1,1 from December 2017, all Macs with T2 chip are shown because T2 was released for the fist time in the iMac Pro.

Anyone using one of those system SMBIOS can choose to use the matching value from the list above for SecureBootModel >> No, they are independent things, SecureBootModel has effect only at boot and it has nothing to do when macOS is running. SMBIOS and SecureBootModel are completely unrelated and do not need to match, Apple Secure Boot model does not depend on the SMBIOS model so there is no point in trying to choose the same. Choose based on the macOS versions you want to boot, or just disable it

They can also use j137 as a default value running High Sierra to Catalina >> yes, anyone must use j137 as a default value running High Sierra (10.13.2) to Catalina.

Anyone running Big Sur needs to use their system value or x86legacy as a default value >> yes, both are valid (even j137) but x86legacy is preferred because it filters macOS 10.15 and older and allows only Big Sur or Monterey (more security).

Anyone running the Monterey Public beta needs to use x86legacy >> yes, that's correct (if you want Apple Secure Boot, of course).

For example my iMac15,1 would use j137 when booting Catalina, but I would need to switch to x86legacy when booting Big Sur with OC 0.7.2 >> no, Big Sur can boot with j137 but x86legacy is preferred for security reasons.

Is there a fuller list of systems with corresponding values for all the Apple models containing T2 chips? >> According to Apple, these Mac computers have the Apple T2 Security Chip (they are the same from the OpenCore list):
  • iMac (2020)
  • Mac Pro (2019)
  • Mac Pro (Rack, 2019)
  • Mac mini (2018)
  • MacBook Air (2020)
  • MacBook Air (2019)
  • MacBook Air (2018)
  • MacBook Pro (2020)
  • MacBook Pro (2019)
  • MacBook Pro (2018)
  • iMac Pro (2017).
The part that still confuses me a little is this: j137 is the recommended value for macOS 10.13.2 through 10.15.x. Is that the value everyone running High Sierra 10.13.2 through to Catalina 10.15.7 should use, even when their corresponding Apple system doesn't contain a T2 chip? >> yes, j137 is the default value running High Sierra (10.13.2) to Catalina.

Will x86legacy work in these earlier versions of macOS on non-T2 systems? > no, only in Big Sur and Monterey because it filters Catalina and older.

Addendum

Anyone using a system older than macOS 10.13.2 must set SecureBootModel=Disabled.

Anyone using a macOS version from 10.13.2 to 10.15.x can choose to use a value from the list above for SecureBootModel instead of j137 filtering macOS versions that he wants to run.

All systems, including Monterey, can also boot with SecureBootModel=Disabled.
 
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Edhawk

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@miliuco thanks, got it straight in my head now!
 
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